Linearization of Multichannel Amplifiers Close to Saturation with Improved Efficiency

In this paper an new linearization approach has been applied to the chain of three amplifiers connected in cascade. The second harmonics of the fundamental signals (IM2) together with the fourth-order nonlinear signals (IM4) are led to the output of third amplifier in cascade. The linearization scheme is arranged so that the IM2 signals are extracted at the output of the second amplifier whereas some additional nonlinear component such as MESFET is exploited as the source of IM2+IM4 signals. Generated nonlinear signals are combined, then adjusted in amplitude and phase and put at the third amplifier output. The third amplifier in cascade biased at class-A is harmonically controlled at input and output. This configuration enables high gain of class A amplifier combined with higher-drain efficiency. Consequently, power-aided efficiency is increased. Also, the third- and fifth-order intermodulation products of a complete amplifying system are reduced in a wide range of the input power going close to saturation.